Updated 9:27 p.m.| President Donald Trump pressed Vladimir Putin over Moscow’s alleged meddling in the 2016 U.S. election on Friday, but the Russian president denied involvement each time, Secretary of State Rex Tillerson said.

“They had a very robust and lengthy exchange on the subject,” Tillerson said from Hamburg, Germany, where Trump and 19 other world leaders are attending the G-20 summit. “The president pressed President Putin on more than one occasion regarding Russian involvement. President Putin denied such involvement.”

Trump and Putin agreed that “this is a substantial hindrance” for U.S.-Russia relations, Tillerson said, adding that the two leaders focused on “how do we move forward from here?”

The secretary of State added that it is unlikely that the United States and Russia will ever agree on the matter. Russia’s Foreign Minister Sergey Lavrov confirmed that Trump brought up the issue, according to Russian media reports.

Though Trump brought up what is a sore subject for both leaders, it does not appear to have affected their talks about other matters. They appear to have struck a deal — though tenuous — on Syria.

Tillerson announced the planned cease-fire and sounded an optimistic tone, saying that “what may be different this time” than during past halting of hostilities in parts of the war-torn country is “the level of commitment on the part of the Russian government. They see the situation in Syria transitioning from the defeat of ISIS … to what we do to stabilize Syria once the war against ISIS is won.”

Earlier, the U.S. embassy in Syria tweeted a quote from State Department spokeswoman Heather Nauert stating that the Trump administration was exploring the “possibility of establishing joint mechanisms with Russia for ensuring stability in #Syria.”

Spox Nauert: The U.S. is looking to explore the possibility of establishing joint mechanisms with Russia for ensuring stability in #Syria.

The Trump administration does not believe Syrian President Bashar Assad nor any of his family members can lead the country, Tillerson said, noting that U.S. officials have made that clear to Putin, who is Assad’s most powerful remaining ally.

The Russian television network RT tweeted that “US & Russia agree ceasefire in southwest #Syria,” attributing the information to Lavrov.

Russian officials were quick to put out their version of a meeting summary, with one Russian television network tweeting that the two leaders talked about cybersecurity, Syria, Ukraine, and combating terrorism. The RT network attributed the list of topics directly to Putin.

The meeting went on for nearly two hours longer than planned because they had “such a level of engagement and exchange, neither one of them wanted to stop,” Tillerson said.

U.S. and Russian officials also agreed to establish joint working groups to focus on cybersecurity and noninterference in each other’s electoral processes, the secretary of State said.

As reporters on-site began tweeting that the high-stakes meeting was wrapping up, a former senior American diplomat said its length — it was scheduled to last just a half hour — was likely a good sign.

Nicholas Burns, a former State Department official, said, “It’s good that it went for two and a half hours” because “they need to get to know each other and learn to communicate effectively.”

“There will be crises and misunderstandings ahead of them,” Burns said in a television interview. “They’re going to need to get on the phone and work things out.”

U.S. officials at one point deployed first lady Melania Trump into the room to try and break up the two leaders’ discussion, Tillerson said, noting that the session lasted another hour after she dropped by.

The two leaders, flanked by just a few senior aides and translators, sat just feet apart in a room at the conference center on the sidelines of the summit. The dramatic scene marked the beginning of the most anticipated meeting of U.S. and Russian leaders in some time.

Their meeting for the first time came as a U.S. Justice Department special counsel and two congressional panels are investigating Russia’s 2016 election meddling, and possibly whether Trump obstructed justice in trying to shut down part of the DOJ probe.

Journalists were allowed into the room for opening remarks at the start of the formal diplomatic session. The duo exchanged pleasantries and set a tone of closer U.S.-Russia ties and increased cooperation aimed at yielding “positive” — a word they both used — outcomes for each country.

The U.S. president, however, during his opening statement, did not issue a call for Putin’s government to drop its efforts to meddle in future American elections. He also ignored or did not hear reporters’ shouted questions asking if he intended to bring it up, according to pool reports from Hamburg.

“It’s an honor to be with you,” Trump said to the former KGB officer at the end of his opening remarks.

“President Putin and I have been discussing various things. I think it’s going very well,” Trump said. “We’ve had some very, very good talks. We’re going to have a talk now. And, obviously, that will continue.

“But we look forward to a lot of very positive things happening for Russia, for the Unites States, and for everyone concerned,” he added as they shook hands.

Following the meeting, Senate Intelligence Vice Chairman Mark Warner alluded in a statement to remarks Trump had made a day earlier in Warsaw, Poland, in which he pointed a finger at Russia for its election interference — and possibly “other countries,” too.

“Whatever the President actually told Putin, it would have had much more force if just the day before President Trump had not equivocated about who was behind the unprecedented attack targeting America last fall. It would also have had more force if he had not again criticized the integrity of our intelligence agencies, among whom there is unwavering agreement about Russia’s active interference in the 2016 U.S. presidential election,” the Virginia Democrat said.

During a series of public remarks in Warsaw on Thursday, Trump called on Russia to stop its “destabilizing activities” and support for “hostile regimes.” He also pledged to make the United States an energy-supplying rival to Russia in central and eastern Europe; Moscow uses its large energy sales to exert leverage in that region.

Putin, through a translator, said he spoken to his American counterpart on the telephone several times since Trump took office on Jan. 20, before adding that “a phone conversation is never enough.”

The Russian president expressed a desire for he and Trump to “resolve” a list of issues important to their countries and the broader world, though he did not mention specifics.

One issue nettling the two countries is nuclear-armed North Korea’s continued tests of long-range missiles. On Thursday, Moscow objected to a U.S.-supported United Nations Security Council condemnation of North Korea’s recent missile test.

“I’m delighted to be able to meet you personally, Mr. President,” Putin told Trump as camera shutters snapped. “And I hope as you have said, our meeting will yield positive results.”

Shortly after the meeting began, Evelyn Farkas, a former Pentagon official who specialized in Russia-related matters, called it “already a win in the column for President Putin for sure.”

“For President Putin, the No. 1 thing he wants to do is demonstrate that Russia is on par with the United States,” she said. “And that’s not just for the world, it’s more important for him to demonstrate that to the Russian people.”